Heretofore, a process utilizing plasma etching or plasma CVD is adopted widely in the process of fabricating a semiconductor device such as a DRAM or a microprocessor.
In many apparatuses such as plasma processing apparatuses that perform etching under decompressed states, shower plates having plural fine gas holes formed therein are employed in order to uniformly supply processing gases to objects to be processed. The material of the shower plate is, for example, Si or quartz. During a normal process, the processing gas is supplied to a back surface side of the shower plate (a plane side reverse to an inner side of the processing chamber) and then supplied into the processing chamber via the gas holes formed in the shower plate.
A plasma processing apparatus in which, in order to control the in-plane uniformity of the process shape of an object to be processed, during such a general process, processing gases are divided by distributors and supplied to a gas processing chamber via two gas supply paths which are respectively provided with mass-flow controllers, is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2006-41088.
On the other hand, as one of subjects in processing a semiconductor device, there is given a subject of reducing the number of foreign particles adhering to the object to be processed. For example, when any foreign material particles fall onto a fine pattern of the object during or prior to etching processing, the etching with respect to the portion of the object is locally prevented. As a result, a fault such as disconnection is brought about, thus causing a reduction in the yield of the semiconductor device. For this reason, there have been proposed many methods wherein, for example, the flow of the gas is controlled to thereby control the transport of the foreign material particles and the number of the foreign particles adhering to the object to be processed is reduced.
Incidentally, in a processing apparatus such as a semiconductor device fabricating apparatus which performs predetermined processing under a decompressed state, a processing chamber is returned to an atmospheric pressure state from the decompressed state by supplying vent gas such as nitrogen or dry air into the processing chamber at the time of maintenance such as total cleaning. At this time, the foreign material particles are flown up by the flow of the vent gas and the flown-up foreign material particles are wafted by the flow of the vent gas in the processing chamber and scatter, and there is a problem that, for example, the interiors of the gas pipes of a gas supply system and/or the back side of a shower plate will be contaminated by the foreign material particles. If the gas supply system on the back side of the shower plate, etc. is contaminated by the foreign material particles at the time of the total cleaning, the foreign material particles are scattered into the processing chamber from the gas supply system according to the supply of processing gas during processing of an object to be processed after the total cleaning, and the yield of a semiconductor device may be reduced.
As a method for coping with this, there has been proposed a method in which, as described in, for example, JP-A No. 2006-41088, a high pressure gas is supplied to the side of the processing chamber from the gas supply system during venting, to thereby prevent the foreign material particles from entering.